I have written about apps by this developer before. Intersog writes interactive educational apps for the business community. They are very extensive and well worth the $20 normal price. There are a couple of their apps available for free. I am not sure for how long they will remain free so hurry. Their apps Small Business and Accounting and Finance combine a full-text course book, interactive flashcards and chapter-level self-tests to give you a complete mLearning resource. These are professional apps and must have apps if you want to learn or brush up on your management skills.